Antioxidant composition

ABSTRACT

The present invention provides a stabilising composition, comprising: a) a first phenolic antioxidant comprising one or more phenolic compounds having the structure of formula (I) wherein R 1  is a linear or branched alkyl group having from 12 to 20 carbon atoms; and b) one or more second phenolic antioxidants independently selected from: a mono-hydroxybenzene having lower steric hindrance than the first phenolic antioxidant; a di-hydroxybenzene; and/or a tri-hydroxybenzene.

The present invention concerns a stabilising composition. Thestabilising composition comprises a first phenolic antioxidant and oneor more second phenolic antioxidants with higher activity than the firstphenolic antioxidant. The stabilising composition is particularly usefulfor the stabilisation of polyols and polyurethanes, includingpolyurethane foam.

Polyurethanes constitute a class of polymers with a range of structures,properties and applications. They all have carbamate or urethanelinkages i.e. —NH—C(═O)—O—, and can be made by reacting isocyanates withpolyols. Polyurethanes can be tailored according to the choice ofisocyanate and polyol, the presence of other components, and thereaction conditions. Polyurethanes include thermoplastic materials andthermosetting materials, and are used to produce flexible and rigidfoams, coatings, fibres, moulded products, elastomeric components, sealsand adhesives, amongst other products.

Polyurethanes are susceptible to degradation over time. Preparation orprocessing of the polyurethanes can also bring about or enhancedegradation. One of the main causes of degradation, as with many otherorganic materials, is the reaction with oxygen in a free radicalautoxidation cycle. The formation of free radicals can be triggered orenhanced by exposure of the polyurethane to heat or radiation(particularly UV light), or the reaction of the polymer with othercomponents or impurities. The free radicals may then react with oxygento form peroxy radicals. The peroxy radicals may then react with furtherpolymer species to produce hydroperoxides, which themselves decompose toresult in further reactive free radical species.

This type of polymer degradation is often referred to as scorch. Scorchmay be detected in a polymer product, for example a polyurethane foam,by the appearance of darker regions in the polymer.

Antioxidants are often used to break the polymer degradation cycle, thusreducing the amount of scorch. Some antioxidants, known as primaryantioxidants, are designed to react with peroxy radicals. Otherantioxidants, known as secondary antioxidants, are designed to reactwith hydroperoxides.

Types of primary antioxidants include sterically hindered phenols andaminic compounds, in particular secondary arylamines, for example thosedisclosed in U.S. Pat. No. 4,824,601. It is known to use these two typesof primary antioxidants in combination for the stabilisation ofpolyurethanes.

Our co-pending application GB 1403714.7 discloses a stabilisingcomposition for polymeric materials, in particular polyurethane,comprising at least one secondary arylamine having the formula I:

wherein: the or each R, which may be the same or different,independently denotes an optionally substituted higher aliphatichydrocarbyl group; x and y are each independently from 0 to 5 providedthat at least one of x and y is at least 1; and a phenolic antioxidant,the composition and/or the secondary arylamine being a liquid at ambientconditions and being substantially free from diphenylamine and/or fromlower alkylated diphenylamine antioxidants.

Although stabilising compositions comprising a phenolic component and anaminic component have demonstrated effective in-process stabilisation ofpolyurethanes, in particular good scorch performance, there areregulatory concerns surrounding the use of aminic components in suchcompositions. In particular, there are regulatory concerns surroundingdiphenylamine, which is the precursor for many aminic antioxidants andis often present in aminic antioxidants in residual amounts.

In addition, when exposed to pollutant gases such as oxides of nitrogen,amine-containing stabilising compositions have a tendency to performpoorly with regards to discolouration.

Phenolic antioxidants alone tend not to perform as well asphenolic/aminic stabilising compositions with regards to scorchperformance. Thus, alternatives to amine antioxidants in the stabilisingcomposition have been considered.

One alternative considered in the prior art is a stabilising compositionhaving a phenolic antioxidant and a benzofuranone component such asthose disclosed in EP 1291384. The benzofuranone component acts as a‘booster’ i.e. a non-aminic component which improves the scorchperformance of the stabilising composition beyond the base stabilisationof the phenolic component. However, such benzofuranone components areexpensive. Thus, there is a demand for lower-cost alternatives.

Another alternative considered in the prior art is a stabilisingcomposition having a phenolic antioxidant and 4-tertbutyl catechol.

U.S. Pat. No. 6,676,849 discloses a scorch inhibitor composition for useas an additive in the manufacture of polyurethane foams, comprising: aderivatised di-tert-butyl phenol substituted with an aromatic, aliphaticor aromatic-aliphatic moiety of C₂ or greater, the moiety optionallypossessing combinations of heteroatoms, which optionally may bedimerized; 4-tertbutyl catechol; and optionally phenothiazine.

However, such stabilising compositions tend to be highly emissive, inparticular with regard to volatile organic compounds (VOC). There is nowa strong demand, particularly from the automotive industry, to reducethe amount of VOC emissions from stabilising composition.

Thus, there remains a need for amine-free antioxidant stabilisingcompositions which overcome the above-identified problems associatedwith the prior art compositions, and which satisfy the requirements ofan antioxidant stabilising composition with regard to shelf-life,sensitivity to hydrolysis, in-process stabilisation, scorch protection,colour properties, volatility and protection against light and pollutantgases.

According to a first aspect of the present invention there is provided astabilising composition, comprising:

-   -   a) a first phenolic antioxidant comprising one or more phenolic        compounds having the structure of formula (I):

-   -   -   wherein R₁ is a linear or branched alkyl group having from            12 to 20 carbon atoms; and

    -   b) one or more second phenolic antioxidants independently        selected from:        -   a mono-hydroxybenzene having lower steric hindrance than the            first phenolic antioxidant;        -   a di-hydroxybenzene; and/or        -   a tri-hydroxybenzene.

According to a second aspect of the present invention there is providedthe use of a stabilising composition for stabilising a polyol and/or apolyurethane, the stabilising composition comprising:

-   -   a) a first phenolic antioxidant comprising one or more phenolic        compounds having the structure of formula (I):

-   -   -   wherein R₁ is a linear or branched alkyl group having from            12 to 20 carbon atoms; and

    -   b) one or more second phenolic antioxidants independently        selected from:        -   a mono-hydroxybenzene having lower steric hindrance than the            first phenolic antioxidant;        -   a di-hydroxybenzene; and/or        -   a tri-hydroxybenzene.

According to a third aspect of the present invention there is provided astabilised composition, comprising:

-   -   a) a polyol and/or a polyurethane; and    -   b) a stabilising composition comprising:        -   i. a first phenolic antioxidant comprising one or more            phenolic compounds having the structure of formula (I):

-   -    wherein R₁ is a linear or branched alkyl group having from 12        to 20 carbon atoms; and        -   ii. one or more second phenolic antioxidants independently            selected from:            -   a mono-hydroxybenzene having lower steric hindrance than                the first phenolic antioxidant;            -   a di-hydroxybenzene; and/or            -   a tri-hydroxybenzene.

The description that follows is applicable, where appropriate, to thefirst, second and third aspects of the present invention.

In this context, the term ‘stabilising composition’ means an antioxidantstabilising composition.

The inventors of the present invention have surprisingly found that astabilising composition comprising a first phenolic antioxidantcomprising one or more phenolic compounds having the structure shown,and one or more second phenolic antioxidants independently selected froma mono-hydroxybenzene having lower steric hindrance than the firstphenolic antioxidant, a di-hydroxybenzene and/or a tri-hydroxybenzene,can be used to stabilise a polyol and/or a polyurethane.

Advantageously, the stabilising compositions of the present inventionhave good hydrolytic stability, particularly when compared to industrybench-mark stabilising compositions including a phenolic antioxidant anda phosphite antioxidant. Thus, the stabilising compositions of thepresent invention are not limited to use as ‘post-treatment’ additivesduring polyurethane production, for example the stabilising compositionmay be added to the precursor polyol.

Further advantageously, the stabilising compositions of the presentinvention have a low contribution to volatile organic compounds (VOC)and low gaseous and condensable emissions (FOG). This may, at least inpart, be due to the minimal volatile emissions (VOC and FOG) from thefirst phenolic antioxidant.

In addition, the stabilising compositions of the present invention havea high level of scorch protection. Without wishing to be bound by anysuch theory, it is believed that the presence of the one or more secondphenolic antioxidants increases the activity of the stabilisingcomposition with regards to scorch protection. More specifically, theone or more second phenolic antioxidants may be a mono-hydroxybenzenehaving lower steric hindrance than the first phenolic antioxidant, adi-hydroxybenzene and/or a tri-hydroxybenzene. All of these componentshave a higher activity with regards to scorch protection than thesterically hindered first phenolic antioxidant. Thus, when the one ormore second phenolic antioxidants are added to the first phenolicantioxidant, the activity of the stabilising composition with regards toscorch protection, is increased.

It has unexpectedly been found that the above advantages of thestabilising composition, in particular the high level of scorchperformance, can be realised without the use of an aminic component i.e.the stabilising composition of the present invention does not containany aminic component. This is beneficial since there are regulatoryconcerns surrounding the use of aminic components in stabilisingcompositions, as outlined above.

The first phenolic antioxidant comprises one or more phenolic compoundshaving the structure of formula (I):

wherein R₁ is a linear or branched alkyl group having from 12 to 20carbon atoms.

Preferably, R₁ is a linear or branched alkyl group having from 12 to 15carbons atoms. More preferably, R₁ is a linear or branched alkyl grouphaving from 13 to 15 carbon atoms.

Preferably, the first phenolic antioxidant comprises a mixture of two ormore phenolic compounds having the structure of formula (I), wherein R₁is different in each phenolic compound.

The first phenolic antioxidant may comprise a mixture of two or morephenolic compounds having the structure of formula (I), wherein R₁ isdifferent in each phenolic compound and is selected from a linear alkylgroup having 12 carbon atoms, a branched alkyl group having 12 carbonatoms, a linear alkyl group having 13 carbon atoms, a branched alkylgroup having 13 carbon atoms, a linear alkyl group having 14 carbonatoms, a branched alkyl group having 14 carbon atoms, a linear alkylgroup having 15 carbon atoms and/or a branched alkyl group having 15carbon atoms.

Preferably, the first phenolic antioxidant comprises a mixture of two ormore phenolic compounds having the structure of formula (I), wherein R₁is different in each phenolic compound and is selected from a linearalkyl group having 13 carbon atoms, a branched alkyl group having 13carbon atoms, a linear alkyl group having 14 carbon atoms, a branchedalkyl group having 14 carbon atoms, a linear alkyl group having 15carbon atoms and/or a branched alkyl group having 15 carbon atoms.

One particularly preferred first phenolic antioxidant comprises C13-C15linear and branched alkyl esters of 3-(3′5′-di-t-butyl-4′-hydroxyphenyl)propionic acid (ANOX® 1315-CAS 171090-93-0).

Advantageously, the first phenolic antioxidant has a low contribution toVOC and FOG. The first phenolic antioxidant may have a lowercontribution to VOC and FOG than other known phenolic antioxidants, forexample 2,6-di-tert-butyl-4-sec-butylphenol (ISONOX® 132-CAS17540-75-9), 2,6-di-tert-butyl-4-nonylphenol (ISONOX® 232-CAS4306-88-1), and benzenepropanoic acid,3,5-bis(1,1-dimethyl-ethyl)-4-hydroxy-, C7-C9 branched alkyl esters(IRGANOX® 1135-CAS 125643-61-0).

The first phenolic antioxidant is preferably a liquid at ambientconditions i.e. at atmospheric pressure (101.325 kPa) and a temperatureof 25° C.

The first phenolic antioxidant may be capable of dissolving the one ormore second phenolic antioxidants. This is particularly advantageouswhere the one or more second phenolic antioxidants is in solid form,since overall a liquid stabilising composition can be achieved. This maybe more easily dispersed within a polymer, for example a polyol and/orpolyurethane.

The one or more second phenolic antioxidants are independently selectedfrom: a mono-hydroxybenzene having lower steric hindrance than the firstphenolic antioxidant; a di-hydroxybenzene; and/or a tri-hydroxybenzene.

By ‘lower steric hindrance’ preferably we mean that the hydroxy groupdirectly attached to the benzene ring in the mono-hydroxybenzene is lesssterically hindered by substituents at one or both of theortho-positions, compared to the first phenolic antioxidant. Forexample, the mono-hydroxybenzene may have substituents at one or both orneither of the ortho-positions, provided that the hydroxy group directlyattached to the benzene ring is less sterically hindered than thehydroxy group in the first phenolic antioxidant.

As outlined previously, the one or more second phenolic antioxidants arebelieved to increase the activity of the stabilising composition, inparticular with regards to scorch protection. Thus, the one or moresecond phenolic antioxidants may be referred to as phenolic ‘booster’antioxidant/component.

The one or more second phenolic antioxidants may be optionallysubstituted.

The mono-hydroxybenzene may be a monomer, a dimer or an oligomer.

The mono-hydroxybenzene dimer may be a bridged bisphenol, for example asulphur-bridged bisphenol or a CR₂-bridged bisphenol. Sulphur-bridgedbisphenols may include 4,4′-thiobis(2-t-butyl-5-methylphenol) (LOWINOX®TBM-6-CAS 96-69-5); and 2,2′-thiobis(6-t-butyl-4-methylphenol) (LOWINOX®TBP-6-CAS 90-66-4). In the CR₂-bridged bisphenol, the R may be hydrogen,for example 2,2′-methylenebis(6-nonyl-p-cresol) (NAUGAWHITE®-CAS7786-17-6).

Preferably, the mono-hydroxybenzene is selected from α-tocopherol;4,4′-thiobis(2-t-butyl-5-methylphenol) (LOWINOX® TBM-6-CAS 96-69-5);2,2′-thiobis(6-t-butyl-4-methylphenol) (LOWINOX® TBP-6-CAS 90-66-4);2,2′-methylenebis(6-t-butyl-4-methylphenol) (LOWINOX® 22M46-CAS119-47-1); 4,4′-butylidenebis[2-t-butyl-5-methylphenol] (LOWINOX®44625-CAS 85-60-9); 2,2′-methylenebis(6-nonyl-p-cresol) (NAUGAWHITE®-CAS7786-17-6); and/or phenol, 4-methyl-, reaction products withdicyclopentadiene and isobutylene (LOWINOX® CPL-CAS 68610-51-5).

The phenol, 4-methyl-, reaction products with dicyclopentadiene andisobutylene (LOWINOX® CPL-CAS 68610-51-5) preferably have the followingstructure:

Preferably, the di-hydroxybenzene is selected from 4-tert-butylcatechol(4-TBC); 2,5-di-tert-amyl-hydroquinone (LOWINOX® AH25-CAS 79-74-3);benzene-1,2-diol (catechol); benzene-1,3-diol (resorcinol); and/orbenzene-1,4-diol (hydroquinone).

The tri-hydroxybenzene may be a pyrogallol i.e. where the hydroxy groupsare positioned at the 1, 2 and 3 positions on the benzene ring; or ahydroxyquinol i.e. where the hydroxy groups are positioned at the 1, 2and 4 positions on the benzene ring.

Preferably, the tri-hydroxybenzene is selected from benzene-1,2,3-triol(pyrogallol); propyl 3,4,5-trihydroxybenzoate (propyl gallate); and/orbenzene-1,2,4-triol (hydroxyquinol).

In one embodiment, the one or more second phenolic antioxidants areindependently selected from:

a di-hydroxybenzene selected from 4-tert-butylcatechol,2,5-di-tert-amyl-hydroquinone, benzene-1,2-diol and/or benzene-1,3-diol;

a tri-hydroxybenzene selected from benzene-1,2,3-triol, propyl3,4,5-trihydroxybenzoate, and/or benzene-1,2,4-triol; and/or

a dimer or oligomer of mono-hydroxybenzene monomers selected from4,4′-butylidenebis[2-t-butyl-5-methylphenol], and/or phenol, 4-methyl-,reaction products with dicyclopentadiene and isobutylene.

The one or more second phenolic antioxidants may be present in an amountof from about 1 to about 50 wt. % based on the total weight of thestabilising composition.

Preferably, the one or more second phenolic antioxidants are present inan amount of from about 1 to about 45 wt. %; from about 1 to about 40wt. %; from about 1 to about 35 wt. %; from about 1 to about 30 wt. %;from about 5 to about 30 wt. %; from about 10 to about 30 wt. %; or fromabout 10 to about 25 wt. %, based on the total weight of the stabilisingcomposition.

By using the one or more second phenolic antioxidants in a relativelysmall amount in the stabilising composition, the contribution of thesecond phenolic antioxidant(s) to VOC and FOG is minimalised.

The stabilising composition is preferably a liquid at ambient conditionsi.e. at atmospheric pressure (101.325 kPa) and a temperature of 25° C.This may provide the advantage of the stabilising composition beingeasily mixed with a polyol and/or a polyurethane.

The inventors of the present invention have developed a stabilisingcomposition combining a low-emissive first phenolic antioxidant and oneor more second phenolic antioxidants which enhance the activity of thestabilising composition. Overall, the stabilising composition of thepresent invention has a low contribution to VOC and FOG and provides ahigh level of scorch protection. It has surprisingly been found that thecontribution to VOC and FOG is significantly lower than the prior artstabilising compositions, particularly those involving a phenolicantioxidant and a ‘booster’ component.

The stabilising composition according to the present invention isparticularly effective at stabilising polyols and/or polyurethanes. Thepolyol and/or polyurethane may be stabilised against oxidative, thermaland/or radiation (for example light e.g. UV light) induced degradation.

The polyol may, for example, comprise a polyether polyol and/or apolyester polyol. The polyol may be a precursor for a polyurethane.

The polyurethane comprises a polyurethane foam.

The amount of stabilising composition in the stabilised composition maybe from about 0.01 to about 10%; from about 0.01 to about 5%; from about0.01% to about 3.5%; or from about 0.01 to about 2% by weight of thepolyol and/or polyurethane.

The invention will now be more particularly described by the followingexamples.

EXAMPLES

Table 1 outlines details relating to different stabilising componentsused in the examples. Hereinafter, the stabilising components will bereferred to using the name given in the ‘component’ column.

TABLE 1 CAS Component Type No. Description Structure ANOX ® 1315Phenolic 171090- 93-0 C13-C15 linear and branched alkyl esters of3-(3′-5′-di-t-butyl-4′- hydroxylphenyl) propionic acid

4-TBC Phenolic booster 98-29-3 4-tertbutyl catechol

LOWINOX ® TBP-6 Phenolic booster 90-66-4 2,2′-thiobis(6-t-butyl-4-methylphenol)

IRGANOX ® 1135 (BASF) Phenolic 125643- 61-0 Benzenepropanoic acid,3,5-bis(1,1-dimethyl- ethyl)-4-hydroxy-,C7-C9 branched alkyl esters

IRGAFOS ® 38 (BASF) Phosphite 145650- 60-8 Bis(2,4-di-tert.-butyl-6-methylphenyl)-ethyl- phosphite

PS-1 (BASF) Booster — 3-(2-acetyl-5- isooctylphenyl)-5-isooctylbenzofuran-2- one

NAUGARD ® PS-30 Amine 68411- 46-1 Butylated, octylated diphenylamine

R = H, butyl, octyl LOWINOX ® TBM-6 Phenolic booster 96-69-54,4′-thiobis(2-t-butyl-5- methylphenol)

The following stabilising compositions are commercially available andmay be considered as industry bench-mark stabilising compositions:

-   -   IRGASTAB® PUR68 (BASF)-7:1:1 blend of IRGANOX® 1135, IRGAFOS® 38        and a benzofuran-2-one (PS-1)

Examples 1 to 4

Preparation of Stabilised Low Density Polyurethane Foams

Three stabilising compositions with the stabilisers shown in Table 2,were prepared by mixing the relative amounts of the stabilisers. Thestabilising compositions of examples 1 and 2 had a phenolic componentand a phenolic booster component, and are in accordance with the presentinvention. Example 3 represents an industry bench-mark stabilisingcomposition involving a phenolic component, a phosphite component and anon-phenolic ‘booster’ component, and is a comparative example. Example4 represents an industry bench-mark stabilising composition involving aphenolic component and an aminic component, and is a comparativeexample.

TABLE 2 Amount (per hundred Example Stabiliser parts polyol) 1 ANOX ®1315 0.405 4-TBC 0.045 2 ANOX ® 1315 0.405 LOWINOX ® TBM-6 0.045 3IRGANOX ® 1135 0.35 IRGAFOS ® 38 0.05 PS-1 0.05 4 ANOX ® 1315 0.225NAUGARD ® PS-30 0.225

For each of the stabilising compositions outlined in Table 2, the amountshown was dissolved in 104.85 g of a polyether polyol (AT300manufactured by Mitsui). To this, 0.79 g of TEGOSTAB® B8229 (Evonik),0.21 g of a solution containing DABCO® 33LV (Air Products) and DABCO®BL11 (Air Products), and 6.53 g of deionised water were added and thereaction mixture stirred vigorously for 30 seconds at 1500 rpm. 0.27 gof tin(II) ethylhexanoate (Sigma Aldrich) was added and the reactionmixture stirred vigorously for 15 seconds at 1500 rpm. 83.2 g ofisocyanate (Bayer, 2,4-toluylene di-isocyanate and 2,6-toluylenedi-isocyanate mixture) was added and the reaction mixture stirredvigorously for 10 seconds at 1500 rpm.

The resulting mixture was poured into a 25 cm×25 cm×25 cm box lined withKraft paper and the exothermic temperature was measured during foamingto a foam block. Each foam block was either a) cured at 95° C. in aconventional oven for 30 minutes and allowed to cool to ambienttemperature, or b) heated in a microwave oven at a pre-determined powerlevel for a pre-determined time to induce temperatures that representedthose experienced in polyurethane foam production, then cured at 95° C.in a conventional oven. The density of the foam block was roughly 20kg/m³.

Foam blocks with the stabilising compositions of examples 1 to 3 weresubjected to step b) above and the discolouration of the foam due toscorch was measured. The discolouration was measured in terms ofYellowness Index (YI). The lower the YI value, the less discolourationand hence the less scorch. The higher the YI value, the greaterdiscolouration and hence the higher scorch. The results are shown inTable 3.

TABLE 3 Example YI Value 1 24.51 2 28.88 3 19.69

It can be seen from the results that the YI values of the foam blocksstabilised with the stabilising compositions according to the presentinvention (examples 1 and 2) are comparable to YI value of the foamblock stabilised with the industry bench-mark stabilising composition(Example 3).

Separate foam blocks with the stabilising compositions of examples 1 to4 were cured at 95° C. in a conventional oven for 30 minutes and allowedto cool to ambient temperature (step a) above). The foam blocks werethen exposed to NOx gases at a temperature of 60° C. in accordance withstandard test method AATCC Test Method 23-2005. The discolouration after2 hours, 3 hours and 4 hours was measured in terms of Yellowness Index(YI). The results are shown in Table 4.

TABLE 4 YI Value YI Value YI Value Example (2 h) (3 h) (4 h) 1 31.8137.35 41.73 2 47.20 54.38 61.60 3 27.06 37.70 43.40 4 44.58 52.64 58.25

Stabilising compositions are known to contribute adversely todiscolouration of polyurethane foams on exposure to pollutant gases, inparticular NOx gases. It can be seen from the results that the YI valuesat 2 hours, 3 hours and 4 hours for the foam blocks stabilised withstabilising compositions according to the present invention, (examples 1and 2) are comparable to YI values of the foam blocks stabilised withthe industry bench-mark stabilising compositions (examples 3 and 4).

Examples 5 to 14

Oxidation Induction Temperature of Stabilised Polyether Polyols

Stabilising compositions according to the present invention have alsobeen shown to stabilise polyether polyols (the precursor to polyurethanefoams).

Ten polyether polyol samples were stabilised using the stabilisingcompositions shown in Table 5. Examples 5 to 11 used stabilisingcompositions in accordance with the present invention. Examples 12 to 14used an industry bench-mark stabilising composition involving a phenoliccomponent, a phosphite component and a non-phenolic ‘booster’ component,and are comparative examples.

Differential scanning calorimetry was used to determine the OxidationInduction Temperature (OIT) of the stabilised polyether polyol samples.The OIT was measured according to standard test method ASTM 3895, anddid not take into account pre-oxidation events. Differential scanningcalorimetry was carried out in oxygen and the temperature ranged from25° C. to 300° C., increasing at a rate of 10° C. per minute. The OITresults are shown in Table 5.

TABLE 5 Amount (per hundred parts OIT Example Stabiliser polyol) (° C.)5 ANOX ® 1315 0.27 184.68 4-TBC 0.03 6 ANOX ® 1315 0.405 190.79 4-TBC0.045 7 ANOX ® 1315 0.54 194.28 4-TBC 0.06 8 ANOX ® 1315 0.27 180.01LOWINOX ® TBP-6 0.03 9 ANOX ® 1315 0.405 184.52 LOWINOX ® TBM-6 0.045 10ANOX ® 1315 0.54 189.15 LOWINOX ® TBP-6 0.06 11 ANOX ® 1315 0.54 195.32LOWINOX ® TBM-6 0.06 12 IRGANOX ® 1135 0.23 183.03 IRGAFOS ® 38 0.03PS-1 0.03 13 IRGANOX ® 1135 0.35 190.06 IRGAFOS ® 38 0.05 PS-1 0.05 14IRGANOX ® 1135 0.47 194.40 IRGAFOS ® 38 0.07 PS-1 0.07

From the results it can be seen that the polyether polyol samplesstabilised with the stabilising composition according to the presentinvention (examples 5 to 11) had comparable OIT values to those samplesstabilised with the industry bench-mark stabilising composition(examples 12 to 14). OIT values are indicative of the likely scorchperformance.

Examples 15 to 23

Discolouration of Stabilised Polyether Polyols

Nine polyether polyol samples were stabilised using the stabilisingcompositions outlined in Table 6. Examples 15 to 20 used stabilisingcompositions in accordance with the present invention. Examples 21 to 23used an industry bench-mark stabilising composition involving a phenoliccomponent, a phosphite component and a non-phenolic ‘booster’ component,and are comparative examples.

Accelerated heat aging was carried out on each of the polyether polyolsamples for 4 hours at 180° C., and the discolouration was measuredusing the Yellowness Index (YI).

TABLE 6 Amount (per hundred parts YI Value Example Stabiliser polyol) (4h) 15 ANOX ® 1315 0.27 6.66 4-TBC 0.03 16 ANOX ® 1315 0.405 10.56 4-TBC0.045 17 ANOX ® 1315 0.54 15.84 4-TBC 0.06 18 ANOX ® 1315 0.27 8.05LOWINOX ® TBP-6 0.03 19 ANOX ® 1315 0.405 10.36 LOWINOX ® TBP-6 0.045 20ANOX ® 1315 0.54 10.97 LOWINOX ® TBM-6 0.06 21 IRGANOX ® 1135 0.23 2.91IRGAFOS ® 38 0.03 PS-1 0.03 22 IRGANOX ® 1135 0.35 4.00 IRGAFOS ® 380.05 PS-1 0.05 23 IRGANOX ® 1135 0.47 4.37 IRGAFOS ® 38 0.07 PS-1 0.07

From the results it can be seen that the polyether polyol samplesstabilised with the stabilising composition according to the presentinvention (examples 15 to 20) showed comparable discolouration to thosesamples stabilised with the industry bench-mark stabilising composition(examples 21 to 23).

Examples 24 to 26

Viscosity and Thermogravimetric Analysis of Stabilising Compositions

Three stabilising compositions with the stabilisers shown in Table 7,were prepared by mixing the relative amounts of the stabilisers.

TABLE 7 Example Stabiliser Relative Amounts 24 ANOX ® 1315 0.9 4-TBC 0.125 ANOX ® 1315 0.9 LOWINOX ® TBP-6 0.1 26 IRGANOX ® 1135 0.45 IRGAFOS ®38 0.05 PS-1 0.05

The dynamic viscosity for each of the stabilising compositions wasdetermined using a Brookfield viscometer. The results are shown in Table8.

TABLE 8 Dynamic Viscosity Example 25° C. 40° C. 60° C. 24 302 88 28 25392 125 40 26 1060 250 53

It is important for the stabilising compositions to be liquids underoperating conditions in order to be easily handled. From the results itcan be seen that the stabilising compositions according to the presentinvention (examples 24 and 25) have viscosities comparable to theindustry bench-mark stabilising composition (Example 26).

Thermogravimetric analysis of each of the stabilising compositions wasdetermined using standard test method ASTM E1131. The results are shownin Table 9.

TABLE 9 ° C. Example 10% wt. loss 25% wt. loss 50% wt. loss 24 179.87247.87 280.02 25 218.82 253.21 278.89 26 206.90 228.78 247.64

Thermogravimetric analysis indicates the thermal stability of astabilising composition. The thermal stability of a stabilisingcomposition is important due to the high temperatures e.g. greater than170° C., that may be experienced during polyurethane production.

From the results it can be seen that the stabilising compositionsaccording to the present invention (examples 24 and 25) have comparablethermal stability to the industry bench-mark stabilising composition(Example 26).

The invention claimed is:
 1. A stabilising composition, comprising: a) afirst phenolic antioxidant comprising a mixture of two or more phenoliccompounds having the structure of formula (I):

wherein R₁ is a linear or branched alkyl group having from 12 to 20carbon atoms, and R₁ is different in each phenolic compound; and b) oneor more second phenolic antioxidants independently selected from thegroup consisting of: a mono-hydroxybenzene having lower steric hindrancethan the first phenolic antioxidant, wherein the mono-hydroxybenzene isselected from the group consisting of α-tocopherol;4,4′-thiobis(2-t-butyl-5-methylphenol);2,2′-thiobis(6-t-butyl-4-methylphenol);2,2′-methylenebis(6-t-butyl-4-methylphenol);4,4′-butylidenebis[2-t-butyl-5-methylphenol];2,2′-methylenebis(6-nonyl-p-cresol); and phenol, 4-methyl-, reactionproducts with dicyclopentadiene and isobutylene; a di-hydroxybenzeneselected from the group consisting of 4-tert-butylcatechol;2,5-di-tert-amyl-hydroquinone; benzene-1,2-diol; benzene-1,3-diol; andbenzene-1,4-diol; and a tri-hydroxybenzene selected from the groupconsisting of benzene-1,2,3-triol; propyl 3,4,5-trihydroxybenzoate; andbenzene-1,2,4-triol, wherein the stabilizing composition does notcontain a benzofuranone-based booster component.
 2. A stabilisingcomposition according to claim 1, wherein R₁ is a linear or branchedalkyl group having from 12 to 15 carbon atoms.
 3. The stabilisingcomposition according to claim 1, wherein R₁ is a linear or branchedalkyl group having from 13 to 15 carbon atoms.
 4. The stabilisingcomposition according to claim 1, wherein R₁ is selected from the groupconsisting of a linear alkyl group having 12 carbon atoms, a branchedalkyl group having 12 carbon atoms, a linear alkyl group having 13carbon atoms, a branched alkyl group having 13 carbon atoms, a linearalkyl group having 14 carbon atoms, a branched alkyl group having 14carbon atoms, a linear alkyl group having 15 carbon atoms, and abranched alkyl group having 15 carbon atoms.
 5. The stabilisingcomposition according to claim 1, wherein R₁ is selected from the groupconsisting of a linear alkyl group having 13 carbon atoms, a branchedalkyl group having 13 carbon atoms, a linear alkyl group having 14carbon atoms, a branched alkyl group having 14 carbon atoms, a linearalkyl group having 15 carbon atoms, and a branched alkyl group having 15carbon atoms.
 6. The stabilising composition according to claim 1,wherein the first phenolic antioxidant comprises C13-C15 linear andbranched alkyl esters of 3-(3′5′-di-t-butyl-4′-hydroxyphenyl) propionicacid.
 7. The stabilising composition according to claim 1, wherein thefirst phenolic antioxidant is a liquid at ambient conditions.
 8. Thestabilising composition according to claim 1, wherein the one or more ofthe second phenolic antioxidants are substituted.
 9. The stabilisingcomposition according to claim 1, wherein the one or more secondphenolic antioxidants are selected from the group consisting of: adi-hydroxybenzene selected from the group consisting of4-tert-butylcatechol, 2,5-di-tert-amyl-hydroquinone, benzene-1,2-diol,and benzene-1,3-diol; a tri-hydroxybenzene selected from the groupconsisting of benzene-1,2,3-triol; propyl 3,4,5-trihydroxybenzoate; andbenzene-1,2,4-triol; and a dimer or oligomer of mono-hydroxybenzenemonomers selected from the group consisting of4,4′-butylidenebis[2-t-butyl-5-methylphenol], and phenol, 4-methyl-,reaction products with dicyclopentadiene and isobutylene.
 10. Thestabilising composition according to claim 1, wherein the one or moresecond phenolic antioxidants is present in an amount of from about 1 toabout 50 wt. % based on the total weight of the stabilising composition.11. The stabilising composition according to claim 1, wherein the one ormore second phenolic antioxidants are present in an amount of from about10 to about 30 wt. %, based on the total weight of the stabilisingcomposition.
 12. The stabilising composition according to claim 1,wherein the stabilising composition is a liquid at ambient conditions.13. A stabilised composition, comprising: a) a polyol; and b) astabilising composition comprising: i. a first phenolic antioxidantcomprising a mixture of two or more phenolic compounds having thestructure of formula (I):

wherein R₁ is a linear or branched alkyl group having from 12 to 20carbon atoms, and R₁ is different in each phenolic compound; and ii. oneor more second phenolic antioxidants independently selected from thegroup consisting of: a mono-hydroxybenzene having lower steric hindrancethan the first phenolic antioxidant, wherein the mono-hydroxybenzene isselected from the group consisting of α-tocopherol;4,4′-thiobis(2-t-butyl-5-methylphenol);2,2′-thiobis(6-t-butyl-4-methylphenol);2,2′-methylenebis(6-t-butyl-4-methylphenol);4,4′-butylidenebis[2-t-butyl-5-methylphenol];2,2′-methylenebis(6-nonyl-p-cresol); and phenol, 4-methyl-, reactionproducts with dicyclopentadiene and isobutylene; a di-hydroxybenzeneselected from the group consisting of 4-tert-butylcatechol;2,5-di-tert-amyl-hydroquinone; benzene-1,2-diol; benzene-1,3-diol; andbenzene-1,4-diol; and a tri-hydroxybenzene selected from the groupconsisting of benzene-1,2,3-triol; propyl 3,4,5-trihydroxybenzoate; andbenzene-1,2,4-triol, wherein the stabilizing composition does notcontain a benzofuranone-based booster component.
 14. The stabilisedcomposition according to claim 13, wherein the polyol comprises apolyether polyol and/or a polyester polyol.
 15. The stabilisedcomposition according to claim 13, wherein the amount of stabilisingcomposition is present from about 0.01 to about 10% by weight of thepolyol.